Mac wont Boot

So last sunday I bought a brand new macbook. the middle range one.
Its been great so far. plays movies, connects to irc, etc etc etc.
So last nite, i decided that since i'm flying out of town today that i would put a few movies on it.
This morning i connect my external hard drive, Copy over a few gigs worth of tv shows. Shut it and come to work.
I get to work and lo and behold it doesn't work.
at all.
First it wouldn't come out of sleep. so i pulled the battery etc. then it booted up. 2 minutes later it froze. So i held the power button and it shut down. and its been doing that since. It either won't boot, as in i push the power button, and it makes the startup noise, and just sits there, or i push it and the screen just stays black.
I'm a brand new mac user and clearly not happy at the moment.
any thoughts would be greatly appreciated.

Try holding "S" while it boots up. Let us know what happens.

Was your hardrive FULL after you put the movies on?

I can't get it to boot now, when i push the power button, the little white light on the front (the one that fades in and out while sleeping) comes on, and stays bright. the screen flickers once and thats it. it stays black.
and it just sits there.
And no its not full, it came with 120 gig HD, on first boot ther ewas like 94 free. i have installed windows and 4 gigs of movies leaving like 83 gigs free.

Edit: I thought i would add, Wednesday Night i added new ram, as in ,i removed the gig that it came with and put 2 gigs in. It worked all of yesterday.
Edit 2: After speaking with my friend, he said (his words) that i had a "kernel panic" meaning it said "You need to restart your computer, please hold the power button"

There's a very big chance the new RAM is causing this. Pull it out and insert the one that was there before this problem started.

Return the faulty RAM if you have a lifetime warranty on it to get it replaced.

BTW, are you sure you bought the right kind of RAM for your MacBook?

Kernel error. Most likely a hardware fault, and since you changed the ram, thats most likely what it is. Take out the ram, blow in the holes and put the rams back in, see if anything happens. If not, put the old ram back in and try and boot.

I just thought I would say, that yes it was the ram. It wasn't seated correctly apparently. I was able to get to the apple store. The funny thing is it worked great for a day. but whatever, lol, works just fine now.
thanks for everyones help